Thanks for the possible identification - Its still there and the sample I removed to photograph i've added to a bowl of water with waterlily. The bowl has remained blanket weed free and the jelly is still there although it hasn't increased.

The linked photo shows very similar material although this isn't attached to anything unlike the linked image........ It's bugging me now that I can't put a name to it !!
Anyone at Liverpool Uni into algae or protozoa ???